You may find the following interesting: http://www.stat.berkeley.edu/~nolan/Papers/dice.pdf http://www.stat.berkeley.edu/~nolan/Papers/dice.pdf They claim that

You may find the following interesting: http://www.stat.berkeley.edu/~nolan/Papers/dice.pdf http://www.stat.berkeley.edu/~nolan/Papers/dice.pdf They claim that a biased coin is impossible via weight distribution.